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manhole or manufactured sediment trap prior to an infiltration basin, and a sediment forebay as <br /> the first cell of a two-cell treatment system. Where the infiltration system captures only clean <br /> runoff(e.g., from a rooftop)pretreatment may not be required. <br /> d) The design shall incorporate a diversion or other method to keep construction site sediment from <br /> entering the infiltration system prior to final stabilization of the entire contributing drainage area. <br /> e) The design shall incorporate provisions, where infiltration practices are proposed, that will <br /> prohibit the compaction of soils by construction equipment. <br /> f) A plan for maintenance of the system must be submitted that identifies the maintenance activities <br /> and frequency of activities for each infiltration practice on the site. A signed maintenance <br /> agreement will be required by the City. <br /> 6) Pond and Additional Infiltration System Design Criteria. Newly constructed or expanded/modified <br /> ponds and basins shall be designed and constructed to meet the following: <br /> a) All ponds or basins shall: <br /> 1) Have a 4:1 maximum slope (above the normal water level [NWL] and below the 10:1 bench, <br /> if a wet pond); <br /> 2) Maximize the separation between inlet and outlet points to prevent short-circuiting of storm <br /> flows; <br /> 3) Have an emergency overflow spillway identified and designed to convey storm flows from <br /> events greater than the 100-year event; and <br /> 4) Be made accessible for maintenance and not be entirely surrounded by steep slopes or <br /> retaining walls which limit the type of equipment that can be used for maintenance. Vehicle <br /> access lane(s) of at least ten (10) feet shall be provided, at a slope less than fifteen percent <br /> (15%) from the access point on the street or parking area to the pond, to accommodate <br /> maintenance vehicles. Maintenance agreements will be required when the pond is not located <br /> on City property. <br /> b) All wet ponds shall: <br /> 1) Have an aquatic bench having a 10:1 (H:V) slope for the first ten (10) feet from the NWL <br /> into the basin; <br /> 2) Have inlets be placed at or below the NWL; <br /> 3) Have a skimming device designed to remove oils and floatable materials up to a five (5) year <br /> frequency event. The skimmer shall be set a minimum of twelve (12) inches below the <br /> normal surface water elevation and shall control the discharge velocity to 0.5 feet per second. <br /> 4) Have an average four (4) feet of permanent pool depth (dead storage depth). This constraint <br /> may not be feasible for small ponds (less than about three [3] acre-feet in volume or less). In <br /> such cases, depths of three to four(3-4) feet may be used. To prevent development of thermal <br /> stratification, loss of oxygen, and nutrient recycling from bottom sediments, the maximum <br /> depth of the permanent pool should be less than or equal to ten (10) feet. <br /> 7) Erosion and Sediment Control (Roseville City Code Chapter 803.04) <br /> a) The City's Erosion Control Ordinance shall be followed for all projects, including those not <br /> regulated under the NPDES construction permit. <br /> Page 6 of 8 12/11/14 <br />